The GridSummary user extension does support remote data (although not documented and not very flexible).

Hi, i'm completely newbie on Sencha things, just starting... I need to build a grid with infinite scroll, large data, and remote group summary, and shows remote summary data on group header, and I read sencha documentation, and examples, but i still can't show remote summary data on groupheader. I don't know how to use ux.Simlets..., ..I need that documantation